High-pressure gear pump

ABSTRACT

A high-pressure gear pump with axial and radial pressure compensation, where the deflection of the gear shafts is accommodated by arranging the bearing blocks in the pump covers so that they can yieldingly deflect to avoid undesirable edge pressures, without sacrificing operational and other advantages.

United States Patent Robert Jung Malsch, Germany 862,581

Aug. 21, 1969 Aug. 31, 1971 Otto Eckerle Aug. 22, 1968 Germany Inventor Appl. No. Filed Patented Assignee Priority H1GH-PRESSURE GEAR PUMP 7 Claims, 7 Drawing Figs.

US. Cl

Int. Cl.

F016 l/l8, FOlc 21/02 Field of Search 171, 182,206; 103/126 A, 126 LB, 126 H; 230/141 A;91/68', 123/12 A; 308/26 Primary Examiner-Carlton R. Croyle Assistant Examiner-John J. Vrablik Attorney0tto John Munz ABSTRACT: A high-pressure gear pump with axial and radial pressure compensation, where the deflection of the gear shafts is accommodated by arranging the bearing blocks in the pump covers so that they can yieldingly deflect to avoid undesirable edge pressures, without sacrificing operational and other advantages.

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' saw u 0F 4 INVENTOR. ROBERT JUNG HIGH-PRESSURE GEAR PUMP BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to a high-pressure gear pump with axial and radial pressure compensation, which consists essen tially of a housing and two spur gears in meshing engagement.

2. Description of the Prior Art Gear pumps have the general characteristic that the gear shafts are subjected to a transversal load resulting from the operating pressure. The result of this is that the shafts, espe-- cially those of high-pressure pumps which are not considerably over-dimensioned, are subject to deflection. The shaft trunnions tend to deform to an inclined position and may thereby cause jamming. The result is an overloading of the edges which can lead to seizure conditions in the journals, or to local overloading of the rolling elements of needle bearings or roller bearings on their inner and outer rolling surfaces. Attempts have been made to eliminate this edge pressure by giving the needless of the needle bearings an arcuate contour, or by grinding the shafts correspondingly. However, this is not a satisfactory solution. It may be possible to avoid the edge pressures, but the shafts still have only point contact with the bearings, so that unfavorable hertzian pressures can occur. The deflection of the shaft causes the additional problem of creating gaps between the gears and the cover faces, with a resultant considerable drop in pressure output and efficiency.

SUMMARY OF THE INVENTION It is an object of the invention to eliminate the edge pressures and to avoid high specific bearing pressures on localized points, thereby increasing the longevity of all moving parts. At the same time, these measures should not result in higher cost and they should not negatively affect the operation and assembly of the device.

The invention proposes to meet the above objective by arranging the bearings of the gear shaft, or gear shafts, for elastic yielding in accordance with the anticipated deflection caused by the hydraulic operating pressure.

This arrangement makes it possible that the bearings adapt themselves to the axis of the deformed shaft, so that high specific bearing pressures on localized points are no longer occurring, and a line contact which may in part even be a surface contact, is established in its place. In addition to this, the elastic design and arrangement of the bearings causes no technical difficulty at all, as the elasticity is easily adjusted by the choice of cross-sectional dimensions and the selection of appropriate materials. I Thus, not only an engineering advantage, but also a commercial advantage is achieved. Furthermore, the assembly is in no way made more difficult. The same can be said for the operational characteristics, the latter remaining unchanged or being even improved, as no disturbing early wear effects occur.

An especially economical and simpleembodiment of the invention consists in having the bearings, or bearing blocks, connected to the covers of the housing by thin ribs on the pressure side only. This design is easily implemented in terms of foundry requirements.

The desired elasticity characteristics of the bearings can also be achieved according to this invention by providing a comparatively heavy rib between the bearing on'the pressure side of the pump and the corresponding edge portion of the cover, and by providing a comparatively thin rib on the admission side of the pump. The thin rib has the advantage that it does not reduce the desired elasticity characteristics, while at the same time providing a support for the bearing.

It is an especially useful arrangement when, according to the invention, the load bearing half of the bearing is separated from the other half of the bearing by a slot andthus is connected to the cover only by the remaining semiannular cross section. This arrangement insures optimal elasticity characteristics, so that the embodiment is. especially advantageous when applied for operation under high pressure. It is also an advantage of this embodiment that the support of the shaft is obtained on a contact surface. In this connection it is also sug gested that the semiannular cross section bechosen of such size that the deflection which is caused by the bearing load corresponds to the deformation of the shaft.

7 BRIEF DESCRIPTION OF THE DRAWINGS In the following, the invention will be explained on the basis of several embodiments illustrated in the drawings as follows:

FIG. I is a schematic cross-sectional illustration of a conventional bearing arrangement of a gear pump shaft;

FIG. 2 is a similar schematic cross-sectional illustration of the support of the gear pump shaft according to the invention;

FIG. 3 is a cross section along the line III-III of FIG. 2;

FIG. 4 is a center cross section through a gear pump according to the invention;

FIG. 5 is a cross section of a modified embodiment of the gear pump;

FIG. 6 is a center cross section of a further modified embodiment of the gear pump;

FIG. 7 is a cross section along the line VII-VII of FIG. 6.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1 is shown a gear shaft 1 which is joumaled in the side covers 2 and 3. All other parts have been omitted to simplify the understanding of the drawing. The hydraulic load caused by the operational pressure is indicated by arrow 4. Under this pressure the shaft 1 deflects and causes edge pressures at the points 5 and 6.

From FIGS. 2 and 3 can be seen that the bearings 7 and 8 are connected to the covers 9 and 10 over the ribs 11 and 12 only, and that the former are positioned at an incline as a result of the axially directed pressure fields l3 and 14. The cross section of the ribs 11 and 12 is chosen such that the deflection angle aW of the deformed shaft corresponds to the deflection angle (11.. of the bearing. In addition to this, the materials selected are such that the ribs 11 and 12 have the necessary elasticity. FIG. 3 shows at 15 the bore provided in the bearing block 16, which is deflected under the axial pressure field 13.

In the embodiment shown in FIG. 4'the cross section of the wall of the cover 17 which carries the bearing 18 is arranged with greatly varying thickness. The rib 19 on the pressure side is made comparatively heavy and the rib 20 on the intake side is made comparatively thin. The wall thicknesses of the two ribs are coordinated in such a manner that the deflection of the cover 17 resulting from the axial load corresponds to the deformation of the shaft.

According to the embodiment shown in FIG. 5 only the load carrying halves 21 and 22 of the bearings are arranged to yield elastically. This is achieved by providing the slots 23 and 24. The elasticity of the bearing is assured through the dimensions chosen for the semiannular cross section linking the bearing halves to the covers, the'deflecting loads 26 and 25 representing also the bearingloads. The lower halves of the bearings, together with the covers 27 and 28, form rigid units which oppose the axial pressure fields 29 in the area of sealing elements and 30.

In the FIGS. 6 and 7 is illustrated a high pressure internal gear pump having needle bearings, the pump consisting primarily of a gear shaft 31 and an internal gear 32 having radial discharge bores 33, a form piece 34 including a support pin 35, a control piston 36, and the axial face plates 37 and 38. The sealing of the device is provided through the radial pressure fields in the area of sealing elements 39 and the axial pressure fields 40 and 41 which are effective on the axial face plates 37 and 38. The axial pressure fields 40 and 41 are backed up by the discs 42 and 43, which in turn are supported over the elastic ribs 44 and 45 of the covers 46 and 47. As a result, the ribs take an inclined position in response to the operating pressure. This assures sealing of the device even under deformations, as both the radial compensation fields and the axial compensation fields cause the establishment of a sealing contact.

What is claimed is: 1. A high-pressure gear pump with pressure compensation in the axial and radial direction, comprising in combination:

a rigid housing, at least two meshing gears rotating inside said housing, at

least one of said gears including a shaft extending from both sides of said gear in the form of a trunnion, I bearing means for each one of said trunnions, said bearing means being yieldingly connected to said rigid housing, so that the axis of said bearing means is forcibly deflectable within the elastic limits of the connection. I 2. A high-pressure gear pump with pressure compensation in the axial and radial direction, comprising in combination:

a rigid housing, at least two meshing gears rotating inside said housing, at

least one of said gears including a shaft extending from both sides of said gear in the form of a trunnion, bearing means for each one of said trunnions, said bearing means being yieldingly connected to said rigid housing, so that the axis of said bearing means is forcibly deflectable within the elastic limits of the connection, said rigid housing further comprising at least one side cover having a rigid main body,and wherein said bearing means has the form of a bearing block, said bearing block being a part of said cover and yieldingly connected to its main body. 3. A high-pressure gear pump as claimed in claim 2, wherein said bearing block is connected to the main body of said side cover by a resiliently yielding riblike flange extending radially from said bearing block, and said riblike flange faces axially the pressure side of the pump.

4. A high-pressure gear pump as claimed in claim 3, wherein said riblike flange extends radially between said bearing block and the main body of said end cover, so that it faces axially both the pressure side and the admission side of the pump; the portion of said flange facing the pressure side representing a comparatively thick wall, and the portion facing the admission side representing a comparatively thin wall.

5. A high-pressure gear pump as claimed in claim 2, wherein said bearing block is longitudinally split by the provision of a slot extending from the gear-facing side of the block over at least a substantial portion of its axial length, thereby defining two bearing halves; and wherein at least one of said bearing halves is yieldingly connected to the main body of said side cover by a riblike flange extending radially from said bearing half at the side facing away from the gears, and said yielding takes place at least partially in that axial portion of said bearing half which defines the transition between it and said flange.

6. A high-pressure gear pump as claimed in claim 5, wherein said yieldingly connected bearing half carries the radial bearing load resulting on its side from the operating pressure; and wherein said transition between the flange and the bearing half has the shape of a ring section.

7. A high-pressure gear pump as claimed in claim 6, wherein the dimensions of said yielding connection and of said transition are selected so that the deflection of said bearing half corresponds substantially to the deflection of the trunnion journaled therein, when both are subjected to the operational load. 

1. A high-pressure gear pump with pressure compensation in the axial and radial direction, comprising in combination: a rigid housing, at least two meshing gears rotating inside said housing, at least one of said gears including a shaft extending from both sides of said gear in the form of a trunnion, bearing means for each one of said trunnions, said bearing means being yieldingly connected to said rigid housing, so that the axis of said bearing means is forcibly deflectable within the elastic limits of the connection.
 2. A high-pressure gear pump with pressure compensation in the axial and radial direction, comprising in combination: a rigid housing, at least two meshing gears rotating inside said housing, at least one of said gears including a shaft extending from both sides of said gear in the form of a trunnion, bearing means for each one of said trunnions, said bearing means being yieldingly connected to said rigid housing, so that the axis of said bearing means is forcibly deflectable within the elastic limits of the connection, said rigid housing further comprising at least one side cover having a rigid main body, and wherein said bearing means has the form of a bearing block, said bearing block being a part of said cover and yieldingly connected to its main body.
 3. A high-pressure gear pump as claimed in claim 2, wherein said bearing block is connected to the main body of said side cover by a resiliently yielding riblike flange extending radially from said bearing block, and said riblike flange faces axially the pressure side of the pump.
 4. A high-pressure gear pump as claimed in claim 3, wherein said riblike flange extends radially between said bearing block and the main body of said end cover, so that it faces axially both the pressure side and the admission side of the pump; the portion of said flange facing the pressure side representing a comparatively thick wall, and the portion facing the admission side representing a comparatively thin wall.
 5. A high-pressure gear pump as claimed in claim 2, wherein said bearing block is longitudinally split by the provision of a slot extending from the gear-facing side of the block over at least a substantial portion of its axial length, thereby defining two bearing halves; and wherein at least one of said bearing halves is yieldingly connected to the main body of said side cover by a riblike flange extending radially from said bearing half at the side facing away from the gears, and said yielding takes place at least partially in that axial portion of said bearing half which defines the transition between it and said flange.
 6. A high-pressure gear pump as claimed in claim 5, wherein said yieldingly connected bearing half carries the radial bearing load resulting on its side from the operating pressure; and whErein said transition between the flange and the bearing half has the shape of a ring section.
 7. A high-pressure gear pump as claimed in claim 6, wherein the dimensions of said yielding connection and of said transition are selected so that the deflection of said bearing half corresponds substantially to the deflection of the trunnion journaled therein, when both are subjected to the operational load. 